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External field characterization using CHAMP satellite data for induction studies

DSpace at IIT Bombay

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Title External field characterization using CHAMP satellite data for induction studies
 
Creator KUNAGU, P
CHANDRASEKHAR, E
 
Subject CHAMP satellite data
magnetosphere
external field characterization
EM induction response
PERIOD GEOMAGNETIC-VARIATIONS
MANTLE BENEATH EUROPE
ELECTRICAL-CONDUCTIVITY
ELECTROMAGNETIC INDUCTION
MAGNETIC-FIELDS
MODEL
EARTH
RESPONSES
CURRENTS
REGION
 
Description Knowledge of external inducing source field morphology is essential for precise estimation of electromagnetic (EM) induction response. A better characterization of the external source field of magnetospheric origin can be achieved by decomposing it into outer and inner magnetospheric contributions, which are best represented in Geocentric Solar Magnetospheric (GSM) and Solar Magnetic (SM) reference frames, respectively. Thus we propose a spherical harmonic (SH) model to estimate the outer magnetospheric contribution, following the iterative reweighted least squares approach, using the vector magnetic data of the CHAMP satellite. The data covers almost a complete solar cycle from July 2001 to September 2010, spanning 54,474 orbits. The SH model, developed using orbit-averaged vector magnetic data, reveals the existence of a stable outer magnetospheric contribution of about 7.39 nT. This stable field was removed from the CHAMP data after transforming to SM frame. The residual field in the SM frame acts as a primary source for induction in the Earth. The analysis of this time-series using wavelet transformation showed a dominant 27-day periodicity of the geomagnetic field. Therefore, we calculated the inductive EM C-response function in a least squares sense considering the 27-day period variation as the inducing signal. From the estimated C-response, we have determined that the global depth to the perfect substitute conductor is about 1132 km and its conductivity is around 1.05 S/m.
 
Publisher INDIAN ACAD SCIENCES
 
Date 2014-10-16T05:29:05Z
2014-10-16T05:29:05Z
2013
 
Type Article
 
Identifier JOURNAL OF EARTH SYSTEM SCIENCE, 122(3)651-660
http://dspace.library.iitb.ac.in/jspui/handle/100/15338
 
Language en